1. Field of the Invention
The present invention relates to a method for introducing drag reducers into fluid transportation systems. The present invention particularly relates to a method for introducing drag reducers into pipelines carrying hydrocarbons.
2. Background of the Art
Hydrocarbon fluids as produced from oil-bearing subterranean formations are typically composed of oil and water. Such fluids may also contain natural gas, and will often contain oil and water insoluble compounds such as clay, silica, waxes, and asphaltenes, which exist as colloidal suspensions. The hydrocarbon fluids, once produced, are transported from the wellsite to refineries by one or more of tanker trucks, pipelines, railcars, and the like.
When transported by pipeline, the force required to move the hydrocarbons through the pipeline must be overcome using pumps. The force which must be overcome to push the hydrocarbon through the pipe, most often described as drag, is desirably reduced as much as possible. Reasons for reducing drag include energy costs associated with running the pumps to overcome the drag and the capital costs of buying and maintaining these pumps. Wear and tear on the pipeline system itself can also be mitigated by reducing drag. Reduction in drag allows for enhanced hydrocarbon production from constrained oil wells.
There have been many types of materials used to reduce drag. For example, U.S. Pat. No. 5,539,044 to Dindi, et al., teaches introducing into the stream a stable, non-agglomerating suspension comprising: (a) water, (b) a substantially insoluble and extremely finely-divided, non-crystalline, ultra-high molecular weight, hydrocarbon-soluble, undegraded polyalkene having 2 to about 30 carbon atoms per alkene precursor, highly dispersed in water, and (c) a small but effective amount of a surfactant having a hydrophilic-lipophilic balance of at least about 9.
In U.S. Pat. No. 5,027,843 to Grabois, et al., it is taught to reduce drag by injecting a water emulsion into the pipeline. The emulsion is prepared using a drag-reducing polymer such as a polyacrylamide polymer. The use of polyalphaolefins or copolymers thereof to reduce the drag of a hydrocarbon flowing through a conduit, and hence the energy requirements for such fluid hydrocarbon transportation, is also well known.
The use of these materials, and particularly the polymer materials as drag reducers can be troublesome. Polymers in particular are particularly sensitive to shear forces that can degrade the polymer's ability to act as a drag reducer. It would be desirable in the art of transporting hydrocarbons to introduce drag reducers into a hydrocarbon without materially reducing the effectiveness of the drag reducer.